Further characterization of the insulin receptor glycosidic moiety in rat adipocytes.
Simultaneous or sequential treatment of rat adipocytes with neuraminidase plus beta-galactosidase decreased insulin binding by 43%. No modification was observed with either enzyme individually. alpha-Mannosidase enhanced insulin binding (38%), whereas beta-N-acetylglucosaminidase and alpha-L-fucosidase were ineffective. Lectins that interact with galactose (Ricinus communis I, RCAI), mannose, Lens culinaris agglutinin (LCA), Concanavalin A (Con A) or N-acetylglucosamine (wheat-germ agglutinin, WGA) decreased insulin binding by 43, 57, 59 and 85% respectively. Lectin inhibition was dose-dependent, saturable and prevented by specific monosaccharides. RCAI, LCA, Con A and WGA decreased the insulin dissociation process by 45, 90, 78 and 84% respectively. Lectins specific for sialic acid, terminal galactose, N-acetylgalactosamine or fucose (Limulus polyphemus, peanut, soybean and Ulex I agglutinins) did not modify either insulin binding or dissociation. These results indicate involvement of penultimate D-galactose, internal N-acetyl-D-glucosamine and D-mannose residues in both processes. They suggest that, in rat adipocytes, a glycosidic moiety participates in the insulin-receptor interaction through N-linked oligosaccharides of the 'complex type'.
D000118:Acetylglucosaminidase / Q000378:metabolism; D000273:Adipose Tissue / Q000378:metabolism*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D007328:Insulin / Q000378:metabolism; D037102:Lectins / Q000494:pharmacology; D008297:Male; D008361:Mannosidases / Q000378:metabolism; D009439:Neuraminidase / Q000378:metabolism; D051381:Rats; D011972:Receptor, Insulin / Q000378:metabolism*; D005644:alpha-L-Fucosidase / Q000378:metabolism; D001616:beta-Galactosidase / Q000378:metabolism
D007328:Insulin; D037102:Lectins; D011972:Receptor, Insulin; D008361:Mannosidases; D009439:Neuraminidase; D001616:beta-Galactosidase; D005644:alpha-L-Fucosidase; D000118:Acetylglucosaminidase